1. Field of the Invention
The present invention relates to an image processing apparatus configured to perform a distortion correction processing, and an imaging apparatus having such an image processing apparatus.
2. Description of the Related Art
Any imaging apparatus, such as a digital camera, uses a lens to focus light from an object and thereby form an image on an imaging element. Since the lens produces aberration, the image formed on the imaging element is inevitably distorted and so is not a true representation of the object. In recent years, more and more imaging apparatuses have been developed, which have a distortion correction function. The distortion correction function is a means for correcting distorted images by processing digital image data. Further, various proposals have been made in connection with the distortion correction processing.
For example, Jpn. Pat. Appln. KOKAI Publication No. 2005-44098 discloses a distortion correction processing in which single-frame image data stored in a frame memory is divided into a plurality of blocks (i.e., block lines). In the invention of Jpn. Pat. Appln. KOKAI Publication No. 2005-44098, such an input range of image data as will provide, by correcting the image distortion, image data of block line corresponding to a desired rectangular area is determined prior to the distortion correction processing. After determining the input range of image data, the image distortion is corrected, block line by block line. Thus, the distortion correction processing can be accomplished by using the minimum amount of image data required.
In order to simplify the processing performed in the distortion correction circuit, the input range of image data to input to the distortion correction circuit should be a rectangular area including parts that should be subjected to distortion correction. If image data of the block line corresponding to the rectangular area is input, the lower end of the block line being processed will overlap the upper end of the block line to be processed next. If the overlapping end parts of two adjacent block lines are both processed, the efficiency of processing image data will inevitably decrease.
Jpn. Pat. Appln. KOKAI Publication No. 2002-304624 proposes a technique of avoiding such double processing of image data in the spatial filter processing. In the invention of Jpn. Pat. Appln. KOKAI Publication No. 2002-304624, that part of the intermediate data being processed in a filter processing means, which should also be used in processing the next image segment, is stored in a frame memory (image memory).